From the viewpoint of high intensity and longer operating life, use of a light emitting diode (LED) as an illumination source is considered. U.S. Pat. No. 6,211,626 disclosed an LED light module comprising a heat transfer member and a LED system and thermal connection including a thermally conductive resin. A light source of a liquid crystal display (LCD) and a light source for illuminating the inside or outside of a room are noted as a specific use application.
JP 2007-109656 discloses an invention that uses an LED as a backlight of a LCD. When using such LED for lighting, an LED array is obtained by combining a plurality of colors such as red, blue and green so as to emit white light. An LED is configured with an LED array disposed on a metal core printed circuit board (MCPCB). Generally a MCPCB is joined to a metallic chassis with a thermal interface material (TIM) such as heat conducting sheet and grease to reduce thermal resistance between the MCPCB and the chassis. An LED emits a large amount of heat. The intensity of the LED decreases if the heat radiated from the periphery of the LED is insufficient. Therefore, various means are used to manage and control heat radiation from LEDs. For example, in a conventional LCD having an LED as a light source, heat is radiated from the LED in the following sequence: LED chip to MCPCB, to thermally conductive grease, to aluminum block, to thermally conductive sheet, to aluminum chassis, to thermally conductive grease, and then to a heat sink. In such a device, joining of members, i.e., joining of the MCPCB to the aluminum chassis and joining of the aluminum chassis to the heat sink, is performed by mechanical means such as screw clamping.
However, joining the members by mechanical means increases the amount of time required for assembly, thereby reducing the mass productivity. Moreover, a thermally conductive sheet or thermally conductive grease is usually expensive, which can weaken the cost competitiveness of the product. What is needed is a method for integrating heat transfer members and LEDs in a manner which circumvents the need for mechanical fabrication of the various members.